4NA 2021 N Level Papers 1 & 2

1) Solve 3(x+2) = 4-7x

• x = -0.2

• x = 1.2

• x = -1.5

• x = 0.5

Answer explanation

To solve the equation, first distribute the 3 on the left side to get 3x + 6 = 4 - 7x. Then, combine like terms to get 10x = -2. Finally, divide by 10 to find x = -0.2, which is the correct answer.

2) $Y is shared in the ratio 4 : 5: 3. The largest share is $37.50. Calculate Y.

• $100

• $90

• $75

• $45

Answer explanation

The largest share is $37.50, which corresponds to 5 parts. Therefore, each part is $7.50. Adding all parts together (4+5+3=12) gives $7.50 * 12 = $90 for Y.

3) The population of Singapore at the end of 2018 was 5.792 million.

The population increased by 0.95% during the next year.

Find the population at the end of 2019.

Give your answer in millions correct to 4 significant figures.

• 5.847

• 5.801
• 5.837
• 5.792

4) Find the greatest integer value of y satisfying -4y > 10.

• -3

• -2

• -4

• -5

Answer explanation

To find the greatest integer value of y satisfying -4y > 10, we divide by -4 and remember to flip the inequality sign. -4y > 10 becomes y < -2.5. The greatest integer less than -2.5 is -3.

5a) Water flows through a tap at a rate of 15 litres per minute.

The tap is used to fill a bath with 110 litres of water.

Find the time taken to fill the bath. Give your answers in minutes and seconds.

• 6 minutes 50 seconds

• 8 minutes 10 seconds

• 7 minutes 20 seconds

• 10 minutes 30 seconds

Answer explanation

To fill 110 litres at 15 litres per minute, it takes 110/15 = 7 minutes and 20 seconds.

5b) Change 15 litres per minute into mililitres per second.

• 350

• 250

• 200

• 300

Answer explanation

To convert 15 litres per minute to millilitres per second, we need to multiply by 1000 (since 1 litre = 1000 millilitres) and divide by 60 (since 1 minute = 60 seconds). 15 * 1000 / 60 = 250 millilitres per second.

6) y is inversely proportional to the cube of x.

Given that y = 16 when x = 2, write a formula for y in terms of x.

• y = 64/x^3

• y = 256/x^3

• y = 128/x^3

• y = 32/x^3

Answer explanation

Since y is inversely proportional to the cube of x, the formula is y = k/x^3. Substituting y = 16 and x = 2 gives k = 128. Therefore, the formula is y = 128/x^3.

• 6y(x^2 + 10y^2)

• 3y(2x^2 + 5y^2)

• 2y(3x^2 - 5y^2)

• 2y(3x^2 + 5y^2)

Answer explanation

To factorise 6x^2y + 10y^3, factor out the common factor 2y to get 2y(3x^2 + 5y^2), which is the correct choice.

• 2/3

• 3/4

• 5/2

• -1/2

Answer explanation

To simplify the expression, add the exponents: 3 + (-1/2) = 5/2. Therefore, n = 5/2, which corresponds to the correct answer choice.

• 11
• 10
• -9

• 12